Can someone help in solving this question?

input:

[ {id: 1, parent_id: nil},
 {id: 6, parent_id: 3},
  {id: 2, parent_id: 1},
  {id: 3, parent_id: 1},
  {id: 4, parent_id: 2},
  {id: 5, parent_id: 1}
 ]

output:

{id: 1, parent_id: nil, {id: 2, parent_id: 1, {id: 4, parent_id: 2} }, {id: 3, parent_id: 1, {id: 6, parent_id: 3}}, {id: 5, parent_id: 1}}, {id: 2, parent_id: 1 }